Due nuovi programmi per illustrare i semafori POSIX.

[gapil.git] / sources / message_setter.c

diff --git a/sources/message_setter.c b/sources/message_setter.c
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+/* message_setter.c
+ * 
+ * Copyright (C) 2010 Simone Piccardi
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+/*****************************************************************************
+ *
+ * File message_setter: Set a message in a shared memory segment,
+ * protecting it with a semaphore. 
+ *
+ * Author: S. Piccardi Jan. 2010
+ *
+ *****************************************************************************/
+#include <sys/types.h>   /* primitive system data types */
+#include <sys/stat.h>    /* file characteristics constants and functions */
+#include <dirent.h>      /* directory operation constants and functions */  
+#include <unistd.h>      /* unix standard library */
+#include <stdlib.h>      /* C standard library */
+#include <string.h>     /* C strings library */
+
+#include <semaphore.h>
+#include "Gapil.h"
+/*
+ * Program message_setter
+ *
+ * List files and their size inside a given directory
+ */
+/* Help printing routine */
+void usage(void);
+
+#define MSGMAXSIZE 256
+
+int main(int argc, char *argv[]) 
+{
+    int i, t = 0;
+    sem_t * sem;
+    char *shmname = "messages";
+    char *semname = "messages";
+    void *shm_ptr;
+    /*
+     * Input section: decode command line parameters 
+     * Use getopt function
+     */
+    opterr = 0;         /* don't want writing to stderr */
+    while ( (i = getopt(argc, argv, "hf:s:t:")) != -1) {
+       switch (i) {
+       /* 
+        * Handling options 
+        */ 
+       case 'h':                                            /* help option */
+           printf("Wrong -h option use\n");
+           usage();
+           return -1;
+           break;
+        case 'f':
+            shmname = optarg;
+            break;
+        case 's':
+            semname = optarg;
+            break;
+       case 't':
+           t = strtol(optarg, NULL, 10);
+           break;
+       case '?':                                    /* unrecognized options */
+           printf("Unrecognized options -%c\n",optopt);
+           usage();
+       default:                                       /* should not reached */
+           usage();
+       }
+    }
+    /* ***********************************************************
+     * 
+     *          Options processing completed
+     *
+     *               Main code beginning
+     * 
+     * ***********************************************************/
+    if ((argc - optind) != 1) {          /* There must be remaing parameters */
+       printf("Wrong number of arguments %d\n", argc - optind);
+        usage();
+    }
+    // Get shared memory segment
+    shm_ptr = FindShm(shmname, MSGMAXSIZE);
+    if ( shm_ptr == NULL) {
+       perror("Cannot find shared memory");
+       exit(1);
+    }
+    // open semaphore
+    if ( (sem = sem_open(semname, 0)) == SEM_FAILED ) {
+       perror("Cannot open semaphore");
+       exit(1);
+    }
+    if ( sem_wait(sem) != 0) {
+       perror("cannot use semaphore");
+       exit(1);
+    }
+    strncpy((char *) shm_ptr, argv[optind],  MSGMAXSIZE);
+    printf("Sleeping for %i seconds\n", t); 
+    sleep(t);
+    if ( sem_post(sem) != 0) {
+       perror("cannot release semaphore");
+       exit(1);
+    }
+    exit(0);
+}
+
+/*
+ * routine to print usage info and exit
+ */
+void usage(void) {
+    printf("Program message_setter: put a message in shared memory segment \n");
+    printf("Usage:\n");
+    printf("  message_setter [-h] [-f shmname]  message \n");
+    printf("  -h          print this help\n");
+    printf("  -f shmname   use shmname memory segment\n");
+    printf("  -s semname   use semname semaphore\n");
+    printf("  -n time      seconds to wait\n");
+    exit(1);
+}